Monday, October 14, 2013

Passing TDs, Interceptions and Interference Calls (2000-2012)

Since 2000 (the first season that Pro-Football-Reference.com provides league-wide penalty data) the NFL has implemented rules to protect QBs and receivers that likely benefit passing offense. In 2006 and 2009 the NFL implemented rules against low hits on the QB, and in 2009, 2010, and 2011 the the league adopted rules protecting "defenseless" receivers.(The idea being that QBs and receivers will have an incentive to attempt riskier plays that will grant them more yards/ points; absent the rule change QBs and WRs would have been subjected to a greater possibility of injury from those same risky plays.)

But the decision in 2004 to more stringently enforce the rule prohibiting illegal contact with receivers 5 yards beyond the line of scrimmage would seem to most benefit the passing game as it prevented defensive backs from disrupting the timing on routes and from stopping smaller, faster wide receivers from getting off the line of scrimmage. (In other words, DeSean Jackson is a much more limited wide receiver when CBs with 4+ inches and 40+ pounds can grab and push him for the first ten yards of his route.)

The chart below lists the total passing touchdowns, interceptions and pass interference calls for the entire NFL from 2000 to 2012. (Bear in mind, that there were only 31 NFL teams in the 2000 and 2001 seasons so the totals should appear slightly lower those seasons.) If the 2004 decision to more stringently referee illegal contact after 5 yards did in fact benefit passing then we would expect an increase in passing TDs and a decreases in interceptions in the years following the decision. Presumably, as defensive backs would have to find new ways to accommodate for the change and to prevent big plays there would also likely be an increase in pass interference calls.

The dotted brown line signals 2004, when the league began to more stringently enforce existing illegal contact rules. While there does not appear to be an immediate effect, as expected starting in 2008 passing TDs and interference calls begin to steadily increase and in 2009 interceptions start a gradual decline.

Wednesday, October 9, 2013

NFL Passing and Rushing Yards per Game per Season (1932-2013)

The chart below presents a telling image of how offense has changed in the NFL since the early 1930s (data from Pro-Football-Reference.com). It shows the average passing and running yards per game per team per season from 1932 to 2013 (as of week 5). What began as a running league, was eclipsed by passing in the early 1940s and then became run-dominant again for a period in the mid-1950's. From the late 1950s until the early 1970's the average NFL team passed for around 50 more yards than it ran for per game. For a period of about four seasons in the mid-1970s the NFL maintained a balance between passing and running.

Since the late-1970s passing looks like a historical Chipotle-stock ticker and rushing looks like the target resting heart rate for a healthy 70 year old. This divergence (likely) largely reflect rule changes that the NFL has made over the last 20 years that limit defensive backs' ability to make contact with receivers and that protect receivers and quarterbacks from injurious hits (which, in turn, provides offensive players with less of a disincentive--i.e., injury--to attempt riskier plays). Considering the ratings that high passing offenses generate, and the fact that ground-and-pound running offenses tend to result in more head injuries for offensive and defensive players, which the NFL is now aiming to avoid at all costs, the difference between rushing and passing will likely only continue to grow.